Dual blade chain tensioner with damping

Abstract

The present invention is directed to a blade-type chain tensioner having two shoes and a blade spring, with one shoe adapted to impart tension to a chain and overlapping the other shoe which is connected to the blade spring. The present invention includes a method for assembling a dual blade chain tensioner comprising the steps of providing a blade spring and two shoes, positioning the blade spring into slots in each shoe and then rotating one shoe over the other shoe and towards the blade spring. A temporary locking pin may be attached to hold the assembly together.

I claim: 
     
       1. A chain tensioner comprising: a first shoe attached to a support surface, said first shoe having an upper and lower surface;   a second shoe pivotally attached to a support surface, said second shoe having an upper and lower surface, said upper surface of said second shoe being positioned to impart tension to a chain, said second shoe lower surface overlapping a portion of the supporting surface of first shoe; and   a blade spring engaging the first shoe, and imparting a tension to said first shoe.   
     
     
       2. The chain tensioner of claim 1 wherein said upper surface of said first shoe is arcuately shaped, said lower surface of said second shoe is arcuately shaped, and the lower surface of said second shoe slidably contacts at least a portion of the upper surface of said first shoe. 
     
     
       3. The chain tensioner of claim 2 wherein said tensioner includes a viscous fluid layer between the upper surface of said first shoe and the lower surface of said second shoe. 
     
     
       4. The chain tensioner of claim 1 wherein the second shoe is formed of a plastic material that is capable of deformation when subjected to a load at an elevated temperature. 
     
     
       5. The chain tensioner of claim 4 wherein the first shoe is formed of different material than the second shoe. 
     
     
       6. The chain tensioner of claim 1 wherein each of said upper surfaces of each shoe has a proximal end and a distal end, said proximal end is closer to the attached end of each shoe, each of said upper surfaces having a length defined by the distance between the proximal and distal end, said second shoe length exceeding the length of the first shoe. 
     
     
       7. The chain tensioner of claim 6 wherein said first shoe is fixedly attached to said support surface. 
     
     
       8. The chain tensioner of claim 1 wherein: said first shoe includes a first end that defines a spring slot;   said second shoe includes a first end that defines a spring slot; and   said blade spring includes a first end and second end, wherein the blade spring first end engages the spring slot of the first shoe and the blade spring second end engages the spring slot of the second shoe.   
     
     
       9. The chain tensioner of claim 8 wherein the first end of the first shoe is pivotally attached to a second support opposite the first support. 
     
     
       10. The chain tensioner of claim 9 wherein: the first shoe includes a knurl that depends from the first end and is pivotally attached to a first support to pivot about a fixed axis that extends substantially perpendicular to the shoe, said spring slot being disposed in the knurl;   the second shoe includes a knurl that depends from the first end and is pivotally attached to a second support to pivot about a second fixed axis that extends substantially perpendicular to the shoe, said spring slot being disposed in the knurl; and   the blade spring contacts the lower surface of the first shoe and is substantially spaced apart parallel to the lower surface of the second shoe, with the first shoe being disposed between the blade spring and the second shoe.   
     
     
       11. The chain tensioner of claim 8 wherein said blade spring is arcuately shaped at a first formation radius, said lower surface of the first shoe is arcuately shaped at a second formation radius, with said first formation radius being less than the second formation radius such that when said blade spring is engaged in said spring slots and elastically deformed to approximately correspond to the flatter arcuate shape of said lower surface of said first shoe, said blade spring imparts a spring tension to the shoes. 
     
     
       12. The chain tensioner of claim 2 wherein: said first shoe further includes a chamber, a first end, and a second end;   said second shoe further includes a chamber, a first end, and a second end;   said first blade spring is disposed within said chamber of said first shoe; and   a second blade spring is disposed within said chamber of said second shoe.   
     
     
       13. The chain tensioner of claim 12 wherein the first end of the first shoe is pivotally attached to a first support, the first end of the second shoe is pivotally attached to a second support, with the first support and the second support aligned so that the axes of rotation of the first and second shoes are substantially parallel. 
     
     
       14. The chain tensioner of claim 12 wherein the second end of the first shoe slidably contacts a stop. 
     
     
       15. The chain tensioner of claim 12 wherein said tensioner includes a viscous fluid layer between the upper surface of the first shoe and the lower surface of the second shoe. 
     
     
       16. The chain tensioner of claim 12 wherein said first end of the first shoe and said first end of the second shoe are pivotably mounted on opposing supports such that said second end of the first shoe extends towards said first end of the second shoe, and said second end of the second shoe extends towards said first end of the first shoe. 
     
     
       17. The chain tensioner of claim 12 wherein: said first shoe is formed of a plastic material that is capable of creep deformation when subjected to a load at an elevated temperature, said first end of the first shoe has a bore for pivotal attachment to a first support;   said second shoe is formed of a plastic material that is capable of creep deformation when subjected to a load at an elevated temperature, said first end of the second shoe has a bore for pivotal attachment to a second support;   said first blade spring is arcuately shaped and elastically deformed to impart a spring tension on the first shoe; and   said second blade spring is arcuately shaped and elastically deformed to impart a spring tension on the second shoe.   
     
     
       18. A method for assembling a dual blade type chain tensioner, comprising: providing a rectangular blade spring having a first end and a second end and an arcuate shape;   providing a first tensioner shoe having an upper surface, and a spring slot in a first end attached to a supporting surface;   providing a second tensioner shoe having a lower surface, an upper surface, and a spring slot in a first end pivotally attached to a supporting surface;   positioning a first end of the blade spring into the first shoe spring slot;   positioning a second end of the blade spring into the second shoe spring slot;   rotating a second end of the second shoe over the first shoe towards the blade spring;   overlapping the lower surface of the second shoe over the upper surface of the first shoe; and   deforming the blade spring elastically to correspond to a less arcuate shape.   
     
     
       19. The method of claim 18 further comprising: placing a temporary locking pin against the second shoe to hold said first shoe and said second shoe in position against the tension of the blade spring.